Clinicians and researchers are currently unable to distinguish at diagnosis with sufficient confidence men with indolent prostate cancer (CaP) from those who have aggressive disease. At present, the strongest predictor of lethal CaP is Gleason score. Utilizing gene expression array data, we previously identified a 157 gene mRNA signature that distinguished high from low Gleason score. This signature significantly improved prediction of lethal disease among men with clinically heterogeneous Gleason score 7. The signature may have clinical utility, but before applying it to patients it must be further refined and then tested in biopsy specimens to determine if the predictive accuracy is sufficient to influence treatment decisions at the time of diagnosis. This mRNA study also identified metabolic pathways differentially enriched in high and low grade disease, generating hypotheses for biological mechanisms that may underlie CaP differentiation and clinical progression. Since different types of biological data may add to the mRNA signature as well as provide different biological information, it is worthwhile to further investigate the metabolic pathways identified. We therefore propose to build upon our promising expression profiling findings with the following Specific Aims: 1) Preparation and testing of Gleason signature of lethal disease for clinical use -To determine if the mRNA signature can be applied in the clinic, we will further validate it by testing its predictive accuracy in biopsy specimens at the time of diagnosis. We hypothesize that within Gleason score 7, the signature's ability to predict lethal disease may improve if applied specifically to the grade 3 or grade 4 focus of the tumor 2) Metabolomics bf Gleason grade In tumor as predictor of lethal disease - Our mRNA study identified metabolic pathways (pyrimidine, propanoate, and beta-alanine metabolism) differentially enriched in high and low grade tumors. Our preliminary data suggests these same pathways may be differentially enriched using metabolomic data; we hypothesize that metabolites may themselves be associated with Gleason score and lethal disease. 3) Metabolomics of Gleason grade in serum as biomarker for upgrading - We hypothesize that metabolites in serum associated with Gleason grade may indicate the presence of higher-grade tumor not detected at biopsy and could serve as a biomarker for monitoring disease progression of active surveillance patients.